This invention relates to a method of forming 4,4'-dinitro-2,2'-bis(trifluoromethyl)diphenyl ether (II) from 4-nitro-2-(trifluoromethyl)halobenzenes (I).
Aryl ethers have been formed by reacting aryl halides with phenols under various conditions. Roberts and Turner disclose (J. Chem. Soc., 1925, Vol. 127, p. 2004) that 2, 4-dichloronitrobenzene reacts with phenol in aqueous KOH, at 100.degree. C., to give a quantitative yield of 4-chloro-2-phenoxynitrobenzene.
R. Q. Brewster (Org. Synth. Coll. Vol. 1943, p. 445) teaches the use of copper catalyst to facilitate the reaction of excess phenol, potassium hydroxide and para-nitrochlorobenzene to form para-nitrophenyl ether.
J. D. Reinheimer, et al, disclose (J. Org. Chem., 1957, vol. 22, p. 1743) that 2,4-dinitrofluorobenzene reacts with 8-hydroxyquinoline in acetone, in the presence of triethylamine, to form 8-(2,4-dinitrophenoxy)quinoline.
D. J. Brunelle and D. A. Singleton disclose (Tetrahedron Lett., 1984, 25, p. 3383) that the reaction between sodium phenoxide and either para-fluoronitrobenzene or para-chloronitrobenzene, to form para-dinitrophenyl ether may be conducted in chlorobenzene using a phase transfer catalyst. In this case, the phase transfer catalysts studied were N-alkyl salts of 4-dialkylamino-pyridines.
Singh and Arora disclose (Tetrahedron, 1988, 44, p 2625) that para-chloronitrobenzene dissolved in toluene, may be reacted with solid potassium hydroxide to form para-dinitrodiphenyl ether. The authors observed the reaction only in the presence of catalytic quantities of various glycols. The authors indicate that the glycols act as phase transfer catalysts. The yields of the ether were poor, that is, never higher than 25%, and there was significant formation of para-chloroaniline. The authors performed mechanistic studies which led them to the conclusion that the reaction proceeded by a free radical chain mechanism.
U.S. Pat. No. 4,558,164 discloses a process for preparing a symmetrical dinitrodiphenyl ether from either ortho or para-nitrochlorobenzenes or ortho or para-nitrofluorobenzene, comprising using a polar organic solvent, a potassium salt of a fatty carboxylic acid containing 2 to 20 carbon atoms or a potassium salt of an aromatic carboxylic acid containing 7 to 12 carbon atoms as catalyst, and either sodium or potassium carbonate to react with the para-nitrochlorobenzene. The reaction is carried out at from 150.degree. C. to 210.degree. C. until the ortho or para-nitrochlorobenzene or ortho or para-nitrofluorobenzene reacts. Only aprotic polar solvents are useful and dimethylacetamide is the preferred solvent.
Japanese Patent 61200947 (as abstract in CA 106:156046 and in Derwent Accession number 86-275567/42) discloses a process for the preparation of 3,4'- and 4,4'-dinitrodiphenyl ether. In this process 4-chloronitrobenzene is mixed with a nitrophenol, a hydrogen chloride absorbent such as an alkaline metal hydroxide or bicarbonate, in the presence of 5 to 50 weight percent of the total material of polyethylene glycol of molecular weight 400 to 1000 or its lower alkyl ethers. The entire mixture is heated to a temperature being between 100.degree. C. and 240.degree. C. There is no additional solvent material used.